UPDATED: Gunman opens fire at Los Angeles International Airport

Update, 12:55 p.m.: Federal authorities are telling news outlets the gunman at LAX was a ticketed passenger entering the airport and not a TSA agent, as was reported earlier.

According to the Los Angeles Times, officials now don't believe the gunman had ever worked for TSA.

Police believe the suspect acted alone and was not tied to any known terrorist group, the L.A. Times said.

Update, 12:30 p.m.: Los Angeles airport police and fire officials said in a press conference at noon that they have treated seven patients and transported six to area hospitals but would not confirm whether there were any fatalities.

Patrick Gannon, chief of security at LAX, said the gunman was shot by authorities but would not give any more information, such as whether he was killed and whether he was a TSA official as has been reported. The FBI is conducting the investigation, he said.

The gunman pulled an assault rifle out of a bag and opened fire in the screening area, then continued shooting well into Terminal 3 before he was shot by Los Angeles Airport police, Gannon said.

A gunman armed with a semi-automatic rifle opened fire at the Los Angeles International Airport on Friday, wounding a Transportation Security Administration employee and two others in an attack that frightened passengers and disrupted flights nationwide.

The Los Angeles Times is reporting that the gunman was a TSA employee at the airport. Law enforcement told the Times that the gunman was killed by authorities after he allegedly shot and killed a fellow TSA employee.

Some passengers who already had cleared security rushed onto the tarmac to evacuate, while others were locked down in airport restaurants and lounges. The airport was being swept for precautionary measures and the bomb unit was on scene.

LAPD Assistant Chief Earl Paysinger said the TSA employee was injured and transported to the hospital after the shooting in Terminal 3.

Ronald Reagan UCLA Medical Center said it received “three male victims from the LAX Airport shootings. One arrived in critical condition and two are listed in fair condition.” Air traffic was affected nationwide as the FAA grounded flights that had not yet departed for LAX.

Witness Brian Keech told The Associated Press he heard “about a dozen gunshots” from inside a security gate at the terminal, which has been evacuated.

The Federal Aviation Administration said a “ground stop” was in affect for all flights heading to Los Angeles, meaning planes in any other airport in the country can't take off for the city, although some flights already in the air were allowed to land.

LAX air traffic controller Michael Foote said some flights were still being allowed to depart.

Foote said his colleagues in the control tower saw passengers spilling from the terminal onto the tarmac, “evacuating the building, getting out as fast as they could.” Officers eventually corralled them.

Other travelers described a chaotic scene as airport security staff evacuated terminals, including onto to the tarmac. Hundreds of people remained gathered outside next to airplanes as authorities investigated what happened.

“People started saying there's a shooter, there's a shooter,” said Natalie Morin, a senior at USC who was heading to San Francisco for a graduate school interview.